Needin some advice. Im so scared and stressed...?

Hi everyone im 16yrs old and 15weeks pregnant. I need some advice.. Okay my mother lives in Albuquerque and I live in Carlsbad. Well she has gotten custody of me when my dad passed away. And allowed me live in a different town. Well now being pregnant I dont know how to tell her without her making me move. I live with my bf and were doing good we have been together for 3yrs. I dont want her to make me move cause i would be leaving my family behind and the father of my baby. I wana talk to her in letting me stay where im at. Im doing very good right now I still go to school and everything. I also have alot of help where im at. And up there its just her and her bf and a couple cousins. But down here I have my stepmom and my bf, his dad, aunts, uncles, and very supportive friends... How do I tell her? I know she wants to be apart of his/her life and she will I go up and visit her all the time.